Non-reducing saccharide-forming enzyme, its preparation and uses

Abstract

Disclosed are novel non-reducing saccharide-forming enzyme, and its preparation and uses. The enzyme is obtainable from the culture of microorganisms such as Rhizobium sp. M-11 (FERM BP 4130) and Arthrobacter sp. Q36 (FERM BP-4316), and capable of forming non-reducing saccharides having a trehalose structure when allowed to act-on reducing partial starch hydrolysates. Glucoamylase and α-glucosidase readily yield trehalose when allowed to act on the non-reducing saccharides. These non-reducing saccharides and trehalose are extensively useful in food products, cosmetics and pharmaceuticals.

We claim: 
     
       1. A biologically pure culture of a microorganism which produces an enzyme which forms a non-reducing saccharide having a trehalose structure when allowed to act on a reducing partial starch hydrolysate, which is a microorganism selected from the group consisting of Rhizobium sp. M-11 (FERM BP-4130) and its mutants. 
     
     
       2. A biologically pure culture of a microorganism which produces an enzyme which forms a non-reducing saccharide having a trehalose structure when allowed to act on a reducing partial starch hydrolysate, which is a microorganism selected from the group consisting of Arthrobacter sp. Q36 (FERM BP-4316) and its mutants. 
     
     
       3. A method for decreasing the reducing power of a reducing partial starch hydrolysate comprising contacting a solution containing a reducing partial starch hydrolysate with an enzyme which forms a non-reducing saccharide having a trehalose structure when allowed to act on a reducing partial starch hydrolysate but not on trehalose. 
     
     
       4. The method of claim 3, wherein said reducing partial starch hydrolysate is one or more reducing partial starch hydrolysates having a degree of glucose polymerization of 3 or more. 
     
     
       5. A method according to claim 3 wherein the reducing partial starch hydrolysate is selected from the group consisting of maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose. 
     
     
       6. A process for producing trehalose which comprises: (a) contacting a solution containing a reducing partial starch hydrolysate with an enzyme to form a non-reducing saccharide having a trehalose structure, said enzyme acting on said reducing partial starch hydrolysate but not on trehalose;   (b) contacting the product of step (a) with glucoamylase or α-glucosidase to form trehalose; and   (c) recovering the resultant trehalose.   
     
     
       7. The process of claim 6, wherein the step (b) further includes a step of crystallizing trehalose. 
     
     
       8. The process of claim 7, wherein said trehalose is hydrous- or anhydrous-crystalline trehalose. 
     
     
       9. The process of claim 6, wherein the resultant mixture in the step (b) is further subjected to column chromatography using a strongly-acidic cation-exchange resin to increase the content of trehalose. 
     
     
       10. The process of claim 6, wherein the trehalose structure in said non-reducing saccharide is located in its end unit. 
     
     
       11. The process of claim 10, wherein said non-reducing saccharide is an α-glycosyl trehalose shown by the formula:   G.sub.n -T     wherein the symbol "G" means glucose residue;   the symbol "n" means one or more integers;   and the symbol "T" means α, α-trehalose residue.   
     
     
       12. The process of claim 6, wherein said reducing partial starch hydrolysate is one or more reducing partial starch hydrolysates having a degree of glucose polymerization of 3 or more.